Fetal blood pH is valuable for high-risk care. Clinical evaluation of our patented continuous intrapartum fetal scalp tissue pH/ECG probe (OBpH probe) demonstrated pH can be monitored by our probe in the term fetus. Our aim is to offer OBpH probes designed for the preterm fetus and for the fetus with a very hairy scalp. (Hair hinders seating of the probe.) The dimensions of the current OBpH probe's spiral relate to the PI's study of intrapartum pelvimetry X-Rays in terms pregnancies. (Hochberg, 1981) No other relevant literature was found. Accordingly, during Phase I we will gather, tabulate and analyze the fetal anatomic and clinical data needed to design safe new OBpH probes. And, we will develop clinical criteria for probe selection. Investigators will use intravaginal ultrasound imaging for fetal scalp thickness (FST) measures and they will provide relevant clinical data. Probes will be designed and bench tested. Phase II will include FDA/IDE controlled clinical trials.